1. Field of the Invention
The present disclosure relates to an optical plate, and particularly to a light diffusion plate employed in a direct type backlight module.
2. Description of the Related Art
Referring to FIG. 6, one such direct type backlight module 100 includes a frame 11, a plurality of point light sources 12, a light diffusion plate 13, and a prism sheet 10. The point light sources 12 are regularly arranged on a base of the frame 11. The light diffusion plate 13 and the prism sheet 10 are disposed on the point light sources 12 above a top of the frame 11 in that order. The light diffusion plate 13 includes a plurality of diffusion particles (not shown) configured for diffusing light. The prism sheet 10 includes a transparent substrate 101 and a prism layer 103 formed on a surface of the transparent substrate 101. The prism layer 103 forms a plurality of elongated V-shaped ridges 105.
In use, light from the point light sources 12 enters the diffusion plate 13 and becomes scattered. The scattered light leaves the diffusion plate 13 to the prism sheet 10. The scattered light then travels through the prism sheet 10 and is refracted out at the elongated V-shaped ridges 105 of the prism sheet 10. The refracted light leaving the prism sheet 10 is concentrated at the prism layer 103 and increases the brightness (illumination) of the prism sheet 10. The refracted light then propagates into a liquid crystal display panel (not shown) disposed above the prism sheet 10.
However, although light from point the light sources 12 enters the diffusion plate 13 and becomes scattered, after the light leaves the prism sheet 10, strong light spots of the point light sources 12 often occurs.
In order to reduce or eliminate the strong light spots of the point light sources 12, the backlight module 100 should further include an upper light diffusion film 14 disposed on the prism sheet 10. However, although the upper light diffusion film 14 and the prism sheet 10 are in contact with each other, a plurality of air pockets may still exist around the boundaries of the light diffusion film 14, the prism sheet 10, and the light diffusion plate 13. When the backlight module 100 is in use, light passes through the air pockets, and some of the light undergoes total reflection by the air pockets along one or another of the corresponding boundaries. In addition, the upper light diffusion film 14 may absorb a certain amount of the light from the prism sheet 10. As a result, a brightness of light illumination of the backlight module 100 is reduced.
Additionally, the direct type backlight module 100 is often manufactured in various sections and thus, have to be integrated together. The integration of the various sections of the direct type backlight module 100 often reduces the rigidity and mechanical strength of the direct type backlight module 100. The reduced rigidity and mechanical strength may result in reduced reliability of the direct type backlight module 100.
Therefore, a new light diffusion plate is desired in order to overcome the above-described shortcomings.